Remove pkg:mustache from .packages

Change-Id: I008c1d111efbd22ffc14000cc23280ea7d118488
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/195487
Auto-Submit: Kevin Moore <kevmoo@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Kevin Moore <kevmoo@google.com>
diff --git a/.packages b/.packages
index 7646deb..af07227 100644
--- a/.packages
+++ b/.packages
@@ -66,7 +66,6 @@
 mime:third_party/pkg/mime/lib
 mockito:third_party/pkg/mockito/lib
 modular_test:pkg/modular_test/lib
-mustache:third_party/pkg/mustache/lib
 native_stack_traces:pkg/native_stack_traces/lib
 nnbd_migration:pkg/nnbd_migration/lib
 oauth2:third_party/pkg/oauth2/lib